Manufacture of electrophotographic plates

ABSTRACT

ERIZING THE LIQUID RESIN TO FORM A SOLID PHOTOCONDUCTIVE LAYER INTEGRALLY BONDED TO THE CONDUCTIVE AND TRANSLUCENT INSULATIVE LAYERS.   PHOTOSENSITIVE PLATES ARE PRODUCED BY DEPOSITING A SOLVENT-FREE MIXTURE OF PHOTOCONDUCTIVE MATERIAL DISPERSED IN A LIQUID POLYMERIZABLE RESIN BETWEEN A CONDUCTIVE LAYER AND A TRANSLUCENT INSULATIVE LAYER AND THEREAFTER POLYM-

Feb. 26, 1.974 TAKAO KOMIYA ETAL 3,794,539

MANUFACTURE OF ELECTROPHO'TOGRAPHIC PLATES Original Fi led Sent. 12, 1967 FIG.1

United States Patent Olfice 3,794,539 Patented Feb. 26, 1974 MANUFACTURE OFPIEIAI EI%IS'ROPHOTOGRAPHIC Takao Komiya and Umi Tosaka, Tokyo, Takashi Ihara,

Kawasaki, Takehiko Matsuo, Tokyo, and Katsunobu Ohara, Kawasaki, Japan, assignors to Canon Kabushiki Kaisha, Tokyo, Japan Original application Sept. 12, 1967, Ser. No. 667,257, now

Patent No. 3,687,659. Divided and this application Dec. 16, 1971, Ser. No. 208,809

Claims priority, application Japan, Sept. 22, 1966, 41/62,655; Nov. 21, 1966, 41/76,477 Int. Cl. C09j /00; G03g 5/04 US. Cl. 156-309 5 Claims ABSTRACT OF THE DISCLOSURE Photosensitive plates are produced by depositing a solvent-free mixture of photoconductive material dispersed in a liquid polymerizable resin between a conductive layer and a translucent insulative layer and thereafter polymerizing the liquid resin to form a solid photoconductive layer integrally bonded to the conductive and translucent insulative layers.

This is a division of application Ser. No. 667,257, filed on Sept. 12, 1967 and now US. Pat. No. 3,687,659.

This invention relates to improved electrophotographic plates and more particularly to the improved three-layer photosensitive plates comprising a photoconductive layer interposed between a conductive layer and a translucent insulative layer and to methods for producing such photosensitive plates useful in electrophotographic processes such as the so-called Carlson process, P.I.P. process, other conventional processes or processes developed by the inventors of this invention and described hereinafter.

Conventional electrophotographic processes wherein photosensitive plates of this kind are used, are described in US. Pats. Nos. 3,124,456 issued to T. H. Moore and 3,041,164 issued to R. M. Blakney.

In Pat. No. 3,041,164, the photosensitive plate is prepared by providing a photoconductive layer on a conductive base and by providing the photoconductive layer with a protective overcoating layer, and a static latent image is formed on said overcoating layer by the Carlson process. In Pat. No. 3,124,456, the photosensitive plate is prepared by providing a photoconductive layer comprising CdS or CdSe and binder resin on a conductive base, and by providing a translucent insulative layer thereon. Charging is carried out simultaneously as the original image is irradiated upon the translucent insulative layer side of said photosensitive plate, and a static latent image is formed on the translucent insulative layer by different build-up of charge attributable to different time constants caused by different impedances in the photoconductive layer portions disposed in the light-and-dark portion of the original image.

Three-layer photosensitive plates of this invention are preferably applied to the processes described in copending applications Ser. Nos. 563,899 and 571,538 (Ser. No. 571,538 is now abandoned). Such processes can be summarized as follows. A photosensitive plate having a photoconductive layer interposed between a conductive layer and a translucent insulative layer is used, and the surface of the translucent insulative layer is initially charged, and by the field of such charge, a layer of charge is bound between the photoconductive layer and the translucent insulative layer or in the neighborhood thereof. Then, by the external field of the bound charge, and corona discharge of opposite polarity to the polarity of said initial charge (or AC corona discharge) and simultaneous irradiation of an original image, a static latent image is formed on the surface of the translucent insulative layer. Then light rays are irradiated on the whole surface of the translucent insulative layer to increase the contrast of the static latent image formed on the surface of the translucent insulative layer.

In each of the above cases, a static latent image is formed on the surface of the translucent insulative layer and said static latent image is developed with charged particles (toner). Thereafter the developed image is transferred to copying material, and the transferred image is fixed to produce an electrophotographic image. Therefore, it is possible to make copies on ordinary papers. The produced image has a natural feeling and is as readable as the image of the printed matters and since it is not necessary to use special photosensitive paper such copy is economical. With regard to the photosensitive plate, since the photoconductive layer is coated with a translucent insulative substance, deterioration and fatigue of the surface of the photoconductive layer are prevented without causing appreciable damage or deterioration by physical effects such as friction or pressure by selecting the insulative layer to have high resistivity and resistance to wear. Also, resistance to humidity or various gases is high, and since it is not necessary for the photoconductive layer itself to retain electric charge, it is possible to use highly sensitive photoconductive substance of low resistivity not usable in the conventional Carlson process, and yet remarkably increase sensitivity. Thus, a number of advantages attend use of such three-layer plates. Since electrophotographic processes in which such photosensitive plates are used have many advantages, there have been proposed many applications in addition to the above-mentioned processes, and it is considered that many applications will. be further developed in the future.

However, there is no satisfactory heretofore known method for producing the resin for binding the fine powder photoconductive substances comprising the photoconductive layer, or for producing such photosensitive plates, and at present it is impossible to supply photosensitive plates of sufficiently high quality.

Conventional photosensitive plates are produced by providing a photoconductive layer comprising a dispersion of fine powder photoconductive substances, such as zinc oxide, cadmium sulfide, cadmium selenide or the like in a resin binder, on a conductive layer such as iron or aluminum, and by providing a transluent insulative layer having high resistance to wear, such as polyester resin, polyethylene resin or the like.

As binders for photoconductive substances, shellac, wax or such like natural resin or silicone resin, vinyl resin, phenol resin, polyester resin, vegetable oil, alkyd resin, styrol resin, melamine resin, acrylic acid ester resin, polycarbonate resin or like resins were used. Such conventional photosensitive plates are produced in accordance with the following method. Liquid in the form of paint is prepared by uniformly mixing the fine powder photoconductive substance, the resin binder, and the solvent for said resin, and such liquid is coated on the conductive layer. The translucent insulative layer is laid thereon to form the layers into a single plate. Alternatively, a thermoplastic resin having a low melting point is selected as the binder for the photoconductive substance, and the liquid paint, obtained as mentioned above, is coated on the conductive layer. The coated conductive layer is sufficiently dried, and the translucent insulative layer is laid on the photoconductive layer and is contacted by hot rollers to melt the binder resin and the translucent insulative layer is thus melt-adhered. In another method the translucent insulative layer is adhered by an adhesive after the photosensitive layer is formed on the conductive layer as mentioned above.

In the foregoing first method, the evaporation of a solvent is remarkably difiicult, and thus the method is not practical. In the second method the translucent insulative layer is irregularly spread by heat, producing wrinkles, and it is very difiicult to produce a smooth photosensitive plate. In addition, an organic solvent is evaporated during the drying process, and therefore hygienic troubles and danger of fire are involved. In the third method, undesired wrinkles occur easily on the translucent insulative layer, the thickness of the translucent insulative layer becomes undesirably thicker by the thickness of the adhesive layer, and the sharpness of the produced image is decreased. In all cases where photosensitive plates are prepared by dissolving binder in a solvent, a little amount of the solvent or water or like volatile components remain in the photoconductive layer after the plate is dried, and therefore deterioration of image properties occurs in several months when such plates are exposed to ambient environment.

In each of the conventional methods, it is impossible to simply and safely produce photosensitive plates of sufficiently high quality.

An object of this invention is to provide photosensitive plates having properties overcoming the drawbacks of conventional photosensitive plates, and methods for produc ing the same.

Another object of this invention is to provide photosensitive plates of high sensitivity which produce sharp and fogless images of high contrast, and methods for producing the same.

A further object of this invention is to provide photosensitive plates which have excellent physical properties of hardness, resistance to bending, and sufiicient durability for repeated use and methods for producing the same.

Another object of this invention is to provide photosensitive plates having less change of latent image properties with passage of time and exhibiting constancy over extended periods.

A further object of this invention is to provide methods for producing photosensitive plates in an economical and sanitary manner.

Another object of this invention is to provide methods for producing photosensitive plates easily and safely.

This invention is characterized in that the photoconductive layer, comprising a photoconductive substance and a resin, of an electrophotographic photosensitive plate comprising an underlying conductive layer and an overlying translucent insulative layer is a solid layer prepared by polymerization of a liquid form resin, i.e., a liquid polymerizable resin precursor, of a mixture obtained by dispersing the photoconductive substance into the liquid form polymerizable resin without a solvent. Such mixture is subjected to polymerization of said liquid resin in such state that the mixture is retained with a definite thickness between the conductive layer and the translucent insulative layer in producing the photosensitive plate.

The above objects and other objects and advantages of this invention will be easily and clearly understood from the following detailed explanations of the invention and the drawings.

FIG. 1 shows the fundamental structure of the photosensitive plate of this invention.

FIG. 2 shows a first process for producing photosensitive plates of this invention.

FIGS. 3a and 3b show a further process for producing photosensitive plates of this invention, FIG. 311 being a vertical cross-sectional side view, and FIG. 3b being a horizontal cross-sectional side view of usable apparatus.

In FIG. 1 the photosensitive plate comprises conductive layer 1, photoconductive layer 2 provided between conductive layer 1 and translucent insulative layer 3. Layer 2 is a solid layer prepared by polymerization of a liquid resin mixture in turn prepared by dispersing a photoconductive substance into a liquid polymerizable resin precursor not containing a solvent.

Conductive layer 1 may comprise a plate of an electrostatically conductive substance such as iron, copper, aluminum or like metal, aluminum foil, tin foil or like metal foils, conductive paper or cloth, paper-laminated with metal foil, or a metal layer vacuum-evaporated onto plastic film.

Translucent insulative layer 3 may comprise any material-satisfying three requirements, i.e., high resistance to wear, high electrical resistivity and high capability to retain static charge, and permeability to activating radiation, as for example, the films of polyester resin, polyethylene resin, polyamide resin, polypropylene resin, polyfiuoroethylene resin, or nitric acid ester or acetic acid ester of cellulose or the like.

Photoconductive layer 2 may comprise inorganic photoconductive substances such as the mixture of one or more of the compounds selected from zinc oxide, titanium oxide, lead oxide, cadmium sulfide, cadmium zinc sulfide, cadmium selenate, and the oxides of mercury, antimony, bismuth, thallium, indium, molybdenum, aluminum, tellurium or iodine, or oragnic photoconductive substances such as anthracene or carbazole or imidazole. It is possible to enlarge the spectrum of the photosensitive zone by absorbing sensitizing materials, such as dye-stuffs in the above photoconductive materials. Among the above photoconductive substances, the substances which are preferably used in this invention are activated cadmium sulfide, cadmium selenate or such like highly photoconductive substances, and when these substances are used, it is possible to remarkably increase sensitivity. Zinc oxide is also one of the preferable materials.

The binders forming the photoconductive layer 2 by binding said photoconductive substances dispersed therein may comprise polystyrene resin, acrylic resin, epoxy resin, polyester resin or such like polymerizable liquid resins not containing a solvent.

The polymerizable liquid resin precursors may comprise liquid polymerizable synthetic resin monomer, liquid synthetic resins of lower polymerization but having polymerizability, and mixtures thereof with other resins dissolved thereinto.

The following are examples:

(1) Liquid polymerizable monomers not containing a solvent: Styrene monomer, methacrylic acid ester monomer, epoxy monomer, such as the main component of Shell Epikote (trade name of Shell Chemical Co., Ltd.) 828, etc. I

(2) Polymerizable resins of lower polymerization in the form of liquid not containing a sol-vent: Epoxy resin, such as Shell Epikote 828, containing a small amount of dimer or trimer, Shell Epikote 834, containing a larger amount of dimer or trimer, etc.

(3) Liquid monomer not containing a solvent into which another resin is dissolved: Vinyl type monomer with unsaturated polyester resin dissolved therein, epoxy monomer with vinyl acetate resin or phenol resin dissolved therein, etc.

(4) Liquid form polymerizable resin of lower polymerization not containing a solvent, into which another resin is dissolved: Vinyl acetate resin or phenol resin dissolved in liquid epoxy resin, etc.

According to this invention, the foregoing resins can be used alone or in the form of a mixture with another of these resins. Of these resins epoxy monomers, epoxy resin of .low polymerization, unsaturated alkyd resin dissolved into vinyl type monomer, etc., produce excellent results, and. in the case of epoxy monomer or epoxy resin of lower polymerization, it is possible to carry out the process by using a plasticizer or like diluent.

The photosensitive plate of this invention is, as aforementioned, characterized in that the photoconductive layer thereof comprises a photoconductive substance and resin dispersed system sandwiched between a conductive layer and a translucent insulative layer, and composedof a solid layer prepared by polymerization of a liquid form resin of a mixture of photoconductive substance dispersed in a liquid form polymerizable resin not containing a solvent. The photo-sensitive plate of this invention can be produced in accordance with the following process. A mixture prepared by dispersing fine powder photoconductive substance into the mixture of one or more liquid form polymerizable resins not containing a solvent, as mentioned above, is placed between the conductive layer and the translucent insulative layer, to form a sandwich, the thickness of such photoconductive layer mixture is made uniform and thereafter, polymerization of the liquid form polymerizable resin is accelerated at an appropriate temperature to produce a perfectly solid resin, and the photosensitive plate is thereby obtained.

According to this invention, in order to appropriately adjust the speed of polymerization of the polymerizable resin in producing photosensitive plates, when the polymerization reaction is too slow, a polymerization promoter is added, and when it is too fast, a polymerization inhibitor is added. In case of, such as for example, methyl acrylic acid, Where polymerization is promoted by the energy of radioactive rays, it is possible to control radiation during the time when polymerization is carried out. Also, when the viscosity of polymerizable resin is low, and the -viscosity of the mixture prepared by dispersing the fine powder photoconductive substance thereinto, is low, and is not appropriate for producing the potosensitive plate, prepolymerization is carried out by keeping the mixture at an appropriate temperature to attain desirable viscosity, and thereafter it can be used in producing photosensitive plates. In this case, the polymerizable resin, having been subjected to prepolymerization, is mixed with the fine powder photoconductive substance to prepare the paint form mixture and when the thus-obtained paint form mixture is applied as a coating, the same effect can be obtained.

Photosensitive plates having various properties can be obtained by changing such conditions as quality, mixture ratio, thickness of the conductive layer, of the photoconductive layer composed of the mixture of photoconductive substance and polymerizable resin, and of the translucent insulative layer, and photosensitive plates prepared in accordance with the following conditions, present excellent properties with regard to contrast, sensitivity, sharpness and fogless image, and in addition to these properties, they exhibit satisfactory physical strength.

As the conductive substance, tin foil or aluminum foil whose thickness is from to 3011., is preferable in view of conductivity, tensile strength and flexibility. Of course, in case of the photosensitive plate which does not require flexibility, it is possible to increase such thickness.

As the translucent insulative layer, polyester film whose thickness is from 10 tOBO/L, produces excellent results. When a film whose thickness is below 10 is used, producing the photosensitive plate is difficult, and in carrying out the charging'operation during use, breakdown readily occurs. Protection of the photoconductive layer is accordingly deteriorated, and the durability of the photosensitive plate for repeated use becomes poor. 0n the other hand, when a film whose thickness is above 30a is used, contrast or sharpness of' the obtained image is poor.

As the photoconductive substance, zinc oxide, activated cadmium sulfide ,and cadmium selenate give excellent results, and as the liquid form polymerizable resin not containing a solvent used as a binder for the fine powder photoconductive substance, epoxy monomer, epoxy resin of lower polymerization, and the solution of unsaturated alkyd resin dissolved into vinyl type monomer, provide particularly excellent results. Among these, especially when epoxy resin is used as the binder, and activated cadmium sulfide or cadmium selenate is used as the photoconductive'substance, the ratio of the binder to the photoconductive substance should be within the range from 10 to 20% by weight, and excellent results are obtained. When this ratio goes beyond 20%, the image formed on the photosensitive plate loses sharpnes, foggy images are produced, contrast becomes poor and photosensitivity is deteriorated. When this ratio is below 10%, the viscosity of the mixture of the fine powder of the photoconductive substance is remarkably increased, and producing the photosensitive plate is difficult.

When epoxy resin is used as the binder, excellent results are obtained when an aliphatic amine, aromatic amine, or amine salt is used as the hardening agent, and the hardening speed is appropriate. In this case, the thick ness of the photoconductive layer after completion of polymerization is appropriately from 30 to 200 When it is below 30 the contrast of the image is deteriorated, and when the thickness becomes above 200,44, the contrast of the obtained image is high, but irregular or foggy images result.

When a solution of unsaturated alkyd resin dissolved in vinyl type monomer is used as the binder, and activated cadmium sulfide or cadmium selenate is used as the photoconductive substance, excellent results are obtained when the ratio of the binder to the photoconductive sub stance and the thickness of the photoconductive layer after completion of polymerization are selected as mentioned above.

Examples of vinyl type monomers usable in this invention include styrol, vinyl acetate, methyl methacrylate, and diallylphthalate or the like. Examples of unsaturated alkyd resins include the polycondensation product of maleic acid anhydride, or fumaric acid and ethylene glycol or propylene glycol etc.

When vinyl type monomer with unsaturated alkyd dissolved therein, is used, excellent results and appropriate hardening speed are obtained by using an agent to promote hardening, such as benzoyl peroxide, or methyl ethyl ketone peroxide or such like catalyst, and naphthanic acid cobalt, or dimethyl aniline or such like hardening promoter.

In FIG. 2, rollers 4, 4' are made of metal or synthetic resins having appropriate rigidity and are rotatably supported on parallel shafts 5, 5' spaced by a predetermined interval. Rollers 4, 4 and shafts 5, 5' control the thickness of the photosensitive plate, and the spacing interval therebetween may be set to provide predetermined thickness of the photosensitive plate by adjusting the interval between the shafts 5, 5'. The photosensitive plate is comprised of thin film 6 of conductive substance, thin film 7 of translucent insulative substance, and mixture 8 prepared by dispersing fine powder photoconductive substance in a liquid form polymerizable resin.

Thin film 6 is placed on one of rollers 4, 4', e.g., roller 4, thin film 7 is placed on roller 4', and mixture Sis placed on the concave portion between the two films to be pinched between thin film 6 and thin film 7 and the whole is drawn in the direction shown by the arrow. Thereby, while the thickness of the photoconductive layer is kept uniform, the polymerization of the polymerizable resin is completed, and thus a three-layer photosensitive plate in the form of sandwich with the photosensitive layer pinched between the films is continuously prepared.

For controlling the thickness of the photosensitive plate, in place of the two rollers, other members such as two cutters with round edge can be used, and instead of drawing the photosensitive plate from between two rollers, the photosensitive plate may be fixed, and the two rollers may be moved to produce the photosensitive plate.

In FIG. 3 base plate 9 having appropriate rigidity, such as metal or synthetic resin, is provided, and the photosensitive plate comprises thin layer 16 of conductive substance, mixture 18 prepared by dispersing a photoconductive substance in a liquid form polymerizable resin, and thin layer 17 of translucent insulative substance. Member 10 is provided for controlling the thickness of the photosensitive plate and is in the form of rails made of a rigid substance, each rail being placed on an opposite end of thin layer 16. Cutter form member 11 has a round edge for regulating the thickness of the photosensitive plate as member 11 moves on rail form member 10, and thus a composite member for controlling photosensitive plate thickness is composed of members and 11.

Thin layer 16 is placed on base plate 9, and "on thin layer 16 is placed thin layer 17. The end portion of layer. 17 is fixed on thin layer 16 by tape 12 or the like. Next, mixture 18 obtained by dispersing the fine powder photoconductive substance in a liquid form polymerizable resin not containing a solvent is disposed between said thin layers 16 and 17. Moving cutter member 11 round edge along the upper surface of thin layer 17 on rail form member 10 squeezes the layers in the direction shown by the arrow in FIG. 3a to form mixture 18 in desired thickness between thin layers 16 and 17, and while in this state, polymerization of said polymerizable resin is completed to produce the photosensitive plate.

In place of cutter member 11, roller 4 shown in FIG. 2, can be used, and the same effect is also obtained by fixing cutter member 11 or roller 4 and moving base plate 9 on which the photosensitive plate is placed. The interval between the members 4, 4' or 10, 11 for controlling the thickness of the photosensitive plate may be adjusted by appropriate means (not shown), for advantageously producing photosensitive plates of various thicknesses.

The respective members used in producing the photosensitive plate are not restricted to those shown in the drawing, but may comprise similar members which give the same effects and functions. The following are the examples of photosensitive plates of the invention, but the invention is not restricted to these examples.

EXAMPLE 1 10 g. of cadmium sulfide activated by copper and halogen and having granularity of almost 10,12, 1.2 g. of epoxy resin Epikote (trade name of Shell Chemical Co., Ltd.) mainly composed of monomer, but containing diluent and lower polymerized resin partially containing dimer and 0.12 g. of the hardening agent K61B (trade name of Anchor Chemical Co.), were sufiiciently mixed to prepare the mixture for the photoconductive layer.

As the thin layer of conductive substance; aluminum foil whose thickness is 15p. was used, and as the thin layer of the translucent insulative substance, Mylar (trade name of El. du Pont de Nemours Co., Inc.) film whose thickness is 25,1; was used, and between said two thin layers, said mixture for the photoconductive layer was pinched in accordance with the method for preparing fthe photosensitive plate shown in FIG. 3, and the photosensitive plate was then prepared. In this case, a rail form member whose height was 100 .4 was used in order to make the thickness of the photoconductive layer 75 i The thus-prepared photosensitive plate was maintained at a temperature of 70 C. for two hours, to promote'the hardening reaction of epoxy resin, and then cooled 'to room temperature, and the photosensitive plate was thus completed.

Positive corona discharge of 6 kv. was applied to this photosensitive plate, and then irradiation of a light image was carried out in a dark place, while at the same time, 5.5 kv. of negative corona discharge was applied thereto. Then the whole surface of the photosensitive plate was exposed, and the latent image was developed with toner having negative charge. Copying paper was then pressed against the plate to transfer the powder image thereon, and the transferred powder image was then fixed on the copying paper to provide a printed image.

Such printed image was sharp, the contrast thereof was about 1,500 v., and no fogginess was evident. The sensitivity of the photosensitive plate was remarkably high, and in the process step of light image exposing, and exposure of only 5 to 10 lux per second was sufficient. The photosensitive plate could be used repeatedly after cleaning it with cloth.

The photosensitive plate prepared in accordance with the above-mentioned method has remarkably strong resistance against bending and remarkable hardness of the film of the photoconductive layer when compared with the photosensitive plates of the same kind produced by prior art techniques which use solvent, and therefore the photosensitive plate obtained in this method is not subject, in image transferring processes'or cleaning processes, to physical damage, which is a problem for conventional photosensitive plates.

From a number of experiments carried out in the past, it was known that in the conventional methods in which solvent is used, small amounts of volatile components, such as solvent or Water content, are retained in the photosensitive layer even after drying, and therefore when conventional photosensitive plates are exposed to ambient atmosphere, deterioration of latent image occurs in several months. However, in accordance with the foregoing method forproducing photosensitive plates, when the photosensitive plate was used over and over again, deterioration of the'latent image was not detected, and upon such ambient exposure, no change in the quality of such latent image was observed.

EXAMPLE 2 As in Example 1, a photosensitive plate Was prepared in accordance with the process shown in FIG. 2, and in order to provide photoconductive layer thickness of 75 the spacing interval between the two rollers was set at 115 1., and the photosensitive plate made in sandwich form was drawn therefrom. Such photosensitive plate was completed under the same conditions as in Example 1, and upon use provided excellent printed images.

"EXAMPLE 3 InExample 1, cadmium selenate was used in place of cadmium sulfide and excellent results were obtained in the same manner.

EXAMPLE 4 g. of cadmium sulfide, 15 g. of Rigolac No. 2004 (trade name of Riken Synthetic Resin K.K.), which is a styrene monomer solution of unsaturated alkyd resin, 2 g. of 14% styrene monomer solution of dimethyl aniline as the hardening promoter and 2 g. of benzoyl peroxide paste as the catalyst, were sufliciently mixed to provide the, photoconductive layer mixture. By using this mixture, a photosensitive plate was prepared in accordance with the method shown in FIG. 3 in the same manner as in Example 1-, and hardening of unsaturated alkyd resin was completed by maintaining the photosensitive plate at 15 C. for about 40 minutes, and the photosensitive plate was thus completed.

. On using this photosensitive plate, a printed image was obtained through the same process as in Example 1, and the. obtained image was remarkably sharp, of high contrast, and no fogginess was evident.

EXAMPLE 5 In Example 4, the preparation of the photosensitive plate was carried out in accordance with the method of EIG. 2 with the spacing interval of the two rollers set at 115, to provide a photoconductive layer thickness of 75 4. This photosensitive plate produced excellent images 9 EXAMPLE 7 100 g. of cadmium sulfide, '20 g. of methacrylic acid methyl ester monomer, and 0.4 g. of benzoyl peroxide were sufiiciently mixed to prepare the mixture for the photo conductive layer and using this mixture, a photosensitive plate, made in accordance with the method shown in FIG. 3 as in Example 1, was maintained at 60 C. for

about one hour, and the polymerization of methacrylic acid methyl ester was completed to provide the photosensitive plate. This photosensitive plate was used to produce the printed images by the same process as in Example 1, and the produced printed images were excellent.

EXAMPIJE 8 Epoxy resin Shell Epikote 834, which is mainly composed of the mixture of monomer and dimer, was used, and a photosensitive plate was prepared in the same manner as in Example 1, and printed images produced by the same process, were excellent.

EXAMPLE 9 100 g. of cadmium sulfide, 18 g. of the mixture obtained by dissolving parts of vinyl acetate resin into 100 parts of Epikote 828, and 3.6 g. of the hardening agent H-92 (trade name of Japan Synthetic Industry K.K.) were sufiiciently mixed, to prepare a mixture for the photoconductive layer and by using this, a photosensitive plate was prepared in accordance with the method shown in FIG. 3 in the same manner as in 'Example 1. This photosensitive plate was maintained at 25 C. for 40 hours, and polymerization was completed. In using this photosensitive plate, +8 kv. corona discharge was applied to the translucent insulative layer, and then 6 kv. AC corona discharge was applied thereto and at the same time irradiation of a light image was carried out. Uniform light was thereafter irradiated on the whole surface of the photosensitive plate, and then the static latent image was developed with developer. In order to make image transfer excellent, +6 kv. corona discharge was carried out, and then copying 'paper was pressed against the image surface to carry out image transfer. The printed image transferred on the copying paper was fixed by thermal treatment. The obtained image was remarkably sharp, of high contrast and no fogginess was evident. Developer remaining on the photosensitive plate was cleaned with a cloth, and the photosensitive plate was used repeatedly, and the image on the photosensitive plate was not deteriorated.

As has been explained so far, according to this invention, it is possible to produce photosensitive plates in an economical, safe and sanitary manner, and such plates produce images of high contrast in accordance with the methods for forming images of the preceding examples. The sensitivity thereof is high, no fogginess is evident, and it is possible to produce sharp images. The physical strength of such photosensitive plates is excellent, and resistance against bending is remarkably higher than that of conventional three-layer photosensitive plates.

The durability of the photosensitive plate against change with passage of time and in repeated use is excellent, and in this respect the practical value of the photosensitive plate of this invention is high. Since no solvent is used, there is no likelihood of solvent injury to the human body or of fire and the photosensitive plate of this invention has remarkable eifects.

This invention is not restricted by the descriptions of the specification or the examples, but embraces those im provements or modifications within the spirit of this invention.

What is claimed is:

1. Method of producing an electrophotographic photosensitive plate comprising a photoconductive layer disposed between a conductive layer and a translucent insulative layer comprising the steps of placing a solvent-free layer of a mixture of photoconductive material dispersed in a polymerizable liquid resin between the conductive layer and the insulative layer and thereafter polymerizing the liquid resin to form a solid photoconductive layer integrally bonded to the photoconductive and insulative ayers.

2. Method of producing an electrophotographic photosensitive plate comprising a photoconductive layer disposed between a conductive layer and a translucent insulative layer comprising the steps of forming a solvent-free mixture of a finely-divided photoconductive material dispersed in a polymerizable liquid resin placing said mixture between a conductive layer and a translucent insulative layer disposed between two operational members having a predetermined space therebetween, moving the conductive layer and the translucent layer relative to the operational members to retain a predetermined thickness of said mixture between the conductive layer and the translucent insulating layer and thereafter polymerizing the liquid resin to form a solid photoconductive layer integrally bonded to the photoconductive and insulative layers.

3. Method according to claim 2, wherein the two operational members are a pair of rollers.

4. Method according to claim 2, wherein one operational member is a plane plate and the other operational member is an edge form member.

5. Method according to claim 2, wherein one operational member is a plane plate and the other operational member is a roller.

References Cited UNITED STATES PATENTS 3,251,686 5/1966 Gundlach 96-1 3,393,070 7/1966 'Snelling 961.5 3,438,706 4/1969 Tanaka et a1 35511 OTHER REFERENCES Dessauer et al.: Xerography and Related Processes, New York: Focal Press (1965). pp. 96, 97.

ALFRED L. L'EAVI'IT, Primary Examiner ROBERT A. DAWSON, Assistant Examiner U.S. Cl. X.R. 

